Written problems to be solved by drawing a ray diagram- to scale if necessary 1. A concave shaving mirror has a focal length of 50 cm. Mark’s face is 30 cm from the mirror. ----------a. Draw a scale diagram to show the position, magnification and nature of the image. ----------b. Discuss, with the aid of a ray diagram, why it would not be practical to position your face beyond the focal length of the mirror. 2. Jack has put a convex ‘blind spot’ mirror on his car side mirror. The mirror has a focal length of -20 cm. ----------a. If he looks in the mirror and his face is 20 cm from the mirror, find the position, nature and magnification of the image formed. ----------b. Discuss, with the aid of a ray diagram, why this is termed a 'wide angle' mirror. 3. A pair of reading glasses has focal length 40 cm. ----------a. If you were reading something that was 15 cm from you, find the position, nature and magnification of the image. ----------b. People who need reading glasses can't see things very close to them. By referring to your diagram, explain how these glasses help them. 4. A digital camera has a ‘macro’ mode with a focal length of 100 mm. If an object 20 mm high is placed 300 mm from the camera lens, use a ray diagram to find ----------a. The position of the CCD (sensor array) for the image to be in focus ----------b. The size and nature of the image ----------c. Complete the table below for a converging lens or mirror
----------Position of object
----------Position of image----------
----------Nature of image----------
----------Between f and pole
----------At f
----------Between f and 2f (c in a mirror)----------
----------At 2f
----------Beyond 2f
----------At infinity
----------d. Compact cameras with a ‘zoom’ ability have two lenses. What property of the camera is affected by changing the distance between the lenses? ----------e. By considering the table above, discuss why it is difficult to create a compact camera with a very good macro mode.
Practice question and exemplar at excellence discuss question
Question: When white light is shone through a prism, it is broken up into different colours. Discuss what is causing this. Step 1: identify the key ideas/questions that you need to answer in this question. It is a 'discuss' question so it is excellence; you need to have 3 parts to your answer Key ideas: what is white light What causes colour (what is coloured light) How does the prism change white into coloured Next: write sentences incorporating these key ideas
White light is a mixture of light of all the different colours that we can see. Each different colour of light has a different wavelength – red light has a longer wavelength than blue light. In order from longest to shortest the colours are: red, orange, yellow, green, blue, indigo, violet.
When light passes from air into glass, it is refracted. However, the amount of refraction depends on the wavelength, so red light is bent less than blue light. This means that the different colours emerge at different angles. This causes the colours to separate as they emerge, making a spectru,
1. A concave shaving mirror has a focal length of 50 cm. Mark’s face is 30 cm from the mirror.
----------a. Draw a scale diagram to show the position, magnification and nature of the image.
----------b. Discuss, with the aid of a ray diagram, why it would not be practical to position your face beyond the focal length of the mirror.
2. Jack has put a convex ‘blind spot’ mirror on his car side mirror. The mirror has a focal length of -20 cm.
----------a. If he looks in the mirror and his face is 20 cm from the mirror, find the position, nature and magnification of the image formed.
----------b. Discuss, with the aid of a ray diagram, why this is termed a 'wide angle' mirror.
3. A pair of reading glasses has focal length 40 cm.
----------a. If you were reading something that was 15 cm from you, find the position, nature and magnification of the image.
----------b. People who need reading glasses can't see things very close to them. By referring to your diagram, explain how these glasses help them.
4. A digital camera has a ‘macro’ mode with a focal length of 100 mm. If an object 20 mm high is placed 300 mm from the camera lens, use a ray diagram to find
----------a. The position of the CCD (sensor array) for the image to be in focus
----------b. The size and nature of the image
----------c. Complete the table below for a converging lens or mirror
----------e. By considering the table above, discuss why it is difficult to create a compact camera with a very good macro mode.
Practice question and exemplar at excellence discuss question
Question: When white light is shone through a prism, it is broken up into different colours. Discuss what is causing this.Step 1: identify the key ideas/questions that you need to answer in this question. It is a 'discuss' question so it is excellence; you need to have 3 parts to your answer
Key ideas: what is white light
What causes colour (what is coloured light)
How does the prism change white into coloured
Next: write sentences incorporating these key ideas
White light is a mixture of light of all the different colours that we can see. Each different colour of light has a different wavelength – red light has a longer wavelength than blue light. In order from longest to shortest the colours are: red, orange, yellow, green, blue, indigo, violet.
When light passes from air into glass, it is refracted. However, the amount of refraction depends on the wavelength, so red light is bent less than blue light. This means that the different colours emerge at different angles. This causes the colours to separate as they emerge, making a spectru,